The entire disclosure of Japanese Patent Application No 10-260,657 filed on Sep. 14, 1998, including specification, claims, drawings and summary is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a block and a riparian improvement structure inhabitable for aquatic life. More particularly, the present invention relates to a block to be laid on the bottom surface of a river, lake or sea, etc., or at the shore or ridge thereof, upon embankment construction for foot protection, river protection, breaking of water, water stream control, etc. Moreover, the present invention relates to a riparian improvement structure made of such blocks so as to provide a riparian area such as a river-bed, bottom, shore, bank, etc. of a river, lake or sea, etc. with an environment suitable for habitation and/or growth of aquatic life.
2. Description of the Related Art
Riparian improvement construction work is being carried out in many cases with the object to protect the inhabitants of a riparian area of a river, lake or sea, etc. from flood, high tide, etc. In order to achieve the object, the riparian improvement construction is implemented with the measures, for instance, to expand a water passage of a river, etc. to make a meandering water channel straight so as to allow water to flow faster down to sea, etc. and to flatten rapids or deep pool of a river, lake, sea, etc. so as to allow water to flow smoothly.
The above riparian improvement measures may comprise conventional riparian improvement work for foot protection, river protection, breaking of water, water stream control, etc. The riparian improvement work includes: an old construction process utilizing wood materials composed of sticks, twigs, round timber, etc. or stone materials; and a modern construction process utilizing concrete blocks, etc.
The construction process utilizing wooden materials may comprise tightening a bundle of round timbers or sticks, twigs, etc., sinking the bundle of wooden materials on the bottom of a river, lake, sea, etc., and placing a weight such as cobblestones, etc. on the bundle of the wooden materials sunken, thereby making the earth and sand on the river-bed, etc. unlikely to be exposed directly to a water flow to prevent the earth and sand from being carried or washed away. An alternative construction process may comprise hammering wooden piles into the river-bed, bank, shore, etc. of a river, lake, sea, etc. for bank protection. These construction processes utilizing wooden materials are currently suffering from the growing difficulty of collecting wooden materials such as sticks, twigs, round timbers, etc. Further, these processes have the problems that they require special skills for tightening sticks, twigs, round timbers, etc., into a whole constructed unit and, as a result, a period of construction becomes prolonged and construction costs are made expensive.
On the other hand, a concrete block construction process may comprise laying concrete blocks on the river-bed, shore, bank, etc. of a river, lake, sea, etc. to prevent the earth and sand from being carried or washed away. This construction process has no problems as the construction process utilizing the wooden materials has, so that the concrete block construction process is recently being extensively applied.
Moreover, the concrete block construction process can provide the advantages of shortening a period of construction and withstanding a rapid water stream of a river, etc. at a sufficiently high level of resistance. This construction process, however, suffers from the drawbacks that concrete blocks change the ecological system of the riparian area and the place where they are laid is no longer inhabitable with aquatic life such as fish, crustaceans, e.g., crabs, shrimps, aquatic insects, etc. and suitable for the growth of aquatic plant, etc.
In order to solve the problems inherent in the conventional construction processes, the present invention has the object to provide a block adapted to form a riparian improvement structure that can improve the riparian area of a river, lake, sea, etc. as well as to provide the riparian area with an environment suited for aquatic life to live in or grow.
Further, the present invention has the object to provide the riparian improvement structure suitable for habitation and/or growth of aquatic life in the riparian area of a river, lake, sea, etc.
In order to achieve the object, the present invention provides a block that can form an inhabitable place for aquatic life, a plurality of the blocks being disposed on a structural body inhabitable for aquatic life, which in turn is disposed in the riparian area, such as a bottom, shore, bank, etc. of a river, lake, sea, etc.
Further, the present invention provides a riparian improvement structure comprising a structural body inhabitable for aquatic life disposed in the riparian area of a river, lake, sea, etc. and a plurality of blocks disposed on the structural body, the block in turn being suitable for habitation and/or growth of aquatic life.
The riparian improvement structure according to the present invention can provide an inhabitable place for aquatic life in the riparian area of a river, lake, sea, etc. and protect an environment suitable for the habitation and/or growth of aquatic life. Further, the riparian improvement structure can cover the bottom, shore, bank, etc. of a river, lake, sea, etc. by laying a plurality of the blocks on the structural body as well as accomplish the foot protection, bank protection, wave control, water control, and so on. Moreover, the blocks disposed on the structural body can serve as preventing the structural body from being carried away even if a water flow would become rapid or if a flood, high tide, etc. would occur.
Furthermore, the riparian improvement structure according to the present invention comprises a block interposed between the bottom, shore, etc. of a river, lake, sea, etc. and an inhabitable structural body. The block disposed in this state can also present the effects similar to or identical to the effects that the riparian improvement structure in the previous mode can.
The block according to the present invention may preferably be provided with a water passage that allows water to pass or flow therethrough when it is disposed on or below the inhabitable structural body. The block with this structure can provide an environment in or by itself which is suitable for the habitation and/or growth of aquatic life.
On the other hand, the structural body may be composed of a bundle of a plurality of wooden materials, such as round timbers, sticks, twigs, bamboo, etc. or a plurality of mass bodies such as natural rock, stone, concrete, etc. disposed in a spaced relationship. The structural body can provide an environment suitable for the habitation and/or growth of aquatic life, particularly when combined with the blocks laid on the structural body or interposed between the structural body and the bottom, shore, bank, etc. of a river, lake, sea, etc.
Further, the blocks may preferably be laid for their flow passages to be directed in the water flow direction of the river, lake, sea, etc. and to allow water to flow or pass therethrough along the water direction of the flow of the water in a river, lake, sea, etc. This disposition of the blocks allows water to flow or passage through the riparian improvement structure in the water flow direction to accelerate the exchanges of water within the riparian improvement structure and, at the same time, can always supply the riparian improvement structure with a fresh water having a sufficient amount of dissolved oxygen that is essential to the aquatic life, thereby giving an environment suitable for the habitation and/or growth of aquatic life.
Moreover, the water flow passage of the block may be of a structure in which it is formed on the bottom surface in the form of a groove or a through-hole extending along or substantially parallel to the flow direction of water in a river, lake, sea, etc. The water flow passage of the block allows the water to flow or pass therethrough to provide a fresh water to the riparian improvement structure and accelerate the metabolism of water, thereby making the riparian improvement structure suitable for the habitation and/or growth of aquatic life.
It is further preferred that the blocks are disposed in a relationship spaced in a given distance from each other. Further, the blocks may preferably be disposed so as for the through-hole to become open at a space formed between the adjacent blocks upon laying a plurality of the blocks in the riparian area of a river, lake, sea, etc. The spaced arrangement of the blocks can permit sun light to reach the inside of the riparian improvement structure, thereby promoting aquatic plant to grow thick and consequently providing fish, crustaceans, e.g., crabs, shrimps, aquatic insects, etc. with an inhabitable place.
Moreover, the blocks may preferably be joined with an appropriate joint member such as wires so as for the adjacent blocks to become variable in the relative positions. The joining of the blocks with each other can make the resulting riparian improvement structure integral and more secure so that the function of the riparian improvement structure can be kept effective for a prolonged period of time as time elapse and even after the inhabitable structural body would have become decayed or changed its position.